io.logspace.agent.shaded.quartz.simpl.CascadingClassLoadHelper Maven / Gradle / Ivy
/*
* Copyright 2001-2009 Terracotta, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
*/
package io.logspace.agent.shaded.quartz.simpl;
import java.util.Iterator;
import java.util.LinkedList;
import java.net.URL;
import java.io.InputStream;
import io.logspace.agent.shaded.quartz.spi.ClassLoadHelper;
/**
* A ClassLoadHelper uses all of the ClassLoadHelper
* types that are found in this package in its attempts to load a class, when
* one scheme is found to work, it is promoted to the scheme that will be used
* first the next time a class is loaded (in order to improve performance).
*
*
* This approach is used because of the wide variance in class loader behavior
* between the various environments in which Quartz runs (e.g. disparate
* application servers, stand-alone, mobile devices, etc.). Because of this
* disparity, Quartz ran into difficulty with a one class-load style fits-all
* design. Thus, this class loader finds the approach that works, then
* 'remembers' it.
*
*
* @see io.logspace.agent.shaded.quartz.spi.ClassLoadHelper
* @see io.logspace.agent.shaded.quartz.simpl.LoadingLoaderClassLoadHelper
* @see io.logspace.agent.shaded.quartz.simpl.SimpleClassLoadHelper
* @see io.logspace.agent.shaded.quartz.simpl.ThreadContextClassLoadHelper
* @see io.logspace.agent.shaded.quartz.simpl.InitThreadContextClassLoadHelper
*
* @author jhouse
* @author pl47ypus
*/
public class CascadingClassLoadHelper implements ClassLoadHelper {
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Data members.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
private LinkedList loadHelpers;
private ClassLoadHelper bestCandidate;
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Interface.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
/**
* Called to give the ClassLoadHelper a chance to initialize itself,
* including the opportunity to "steal" the class loader off of the calling
* thread, which is the thread that is initializing Quartz.
*/
public void initialize() {
loadHelpers = new LinkedList();
loadHelpers.add(new LoadingLoaderClassLoadHelper());
loadHelpers.add(new SimpleClassLoadHelper());
loadHelpers.add(new ThreadContextClassLoadHelper());
loadHelpers.add(new InitThreadContextClassLoadHelper());
for(ClassLoadHelper loadHelper: loadHelpers) {
loadHelper.initialize();
}
}
/**
* Return the class with the given name.
*/
public Class loadClass(String name) throws ClassNotFoundException {
if (bestCandidate != null) {
try {
return bestCandidate.loadClass(name);
} catch (Throwable t) {
bestCandidate = null;
}
}
Throwable throwable = null;
Class clazz = null;
ClassLoadHelper loadHelper = null;
Iterator iter = loadHelpers.iterator();
while (iter.hasNext()) {
loadHelper = iter.next();
try {
clazz = loadHelper.loadClass(name);
break;
} catch (Throwable t) {
throwable = t;
}
}
if (clazz == null) {
if (throwable instanceof ClassNotFoundException) {
throw (ClassNotFoundException)throwable;
}
else {
throw new ClassNotFoundException( String.format( "Unable to load class %s by any known loaders.", name), throwable);
}
}
bestCandidate = loadHelper;
return clazz;
}
@SuppressWarnings("unchecked")
public Class loadClass(String name, Class clazz)
throws ClassNotFoundException {
return (Class) loadClass(name);
}
/**
* Finds a resource with a given name. This method returns null if no
* resource with this name is found.
* @param name name of the desired resource
* @return a java.net.URL object
*/
public URL getResource(String name) {
URL result = null;
if (bestCandidate != null) {
result = bestCandidate.getResource(name);
if(result == null) {
bestCandidate = null;
}
else {
return result;
}
}
ClassLoadHelper loadHelper = null;
Iterator iter = loadHelpers.iterator();
while (iter.hasNext()) {
loadHelper = iter.next();
result = loadHelper.getResource(name);
if (result != null) {
break;
}
}
bestCandidate = loadHelper;
return result;
}
/**
* Finds a resource with a given name. This method returns null if no
* resource with this name is found.
* @param name name of the desired resource
* @return a java.io.InputStream object
*/
public InputStream getResourceAsStream(String name) {
InputStream result = null;
if (bestCandidate != null) {
result = bestCandidate.getResourceAsStream(name);
if(result == null) {
bestCandidate = null;
}
else {
return result;
}
}
ClassLoadHelper loadHelper = null;
Iterator iter = loadHelpers.iterator();
while (iter.hasNext()) {
loadHelper = iter.next();
result = loadHelper.getResourceAsStream(name);
if (result != null) {
break;
}
}
bestCandidate = loadHelper;
return result;
}
/**
* Enable sharing of the "best" class-loader with 3rd party.
*
* @return the class-loader user be the helper.
*/
public ClassLoader getClassLoader() {
return (this.bestCandidate == null) ?
Thread.currentThread().getContextClassLoader() :
this.bestCandidate.getClassLoader();
}
}